This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Organisms have evolved a specialized, multi-component protein system to ensure correct FeS cluster assembly. This system includes Fe and S donors, a scaffold for the Fe/S cluster assembly and an Hsp70 chaperone and a J protein cochaperone to facilitate the Fe/S cluster transfer process. While in most eukaryotes the Hsp70 also participates in other processes such protein folding and import, in bacteria and a small subset of fungi it has evolved to function in Fe/S cluster assembly only. As a result of molecular coevolution, the J protein cochaperone in these organisms also became more specialized. The exact nature of this specialization remains unknown however. We hypothesize that structural differences among the cochaperones are partly responsible and are using NMR spectroscopy to determine and thoroughly compare the structures of J proteins from an organism with a general Hsp70 and an organism with a specialized Hsp70. We hope the results of our studies will lend further support to our hypothesis.